Device for reducing pulsation in a variable displacement compressor

Abstract

The present invention is directed to provide a device for reducing pulsation in a variable displacement compressor. The compressor is connected to an external refrigerant circuit. The device for reducing pulsation includes a flow passage and a control valve. The control valve includes a valve housing, a spool valve and a damper chamber. The spool valve has formed therethrough a flow hole. The damper chamber communicates with the flow passage adjacent to the external refrigerant circuit through the flow hole. Effective cross-sectional area and effective length of the flow hole are determined based on frequency of a specific pulsation of the refrigerant gas and volume of the damper chamber at the time of the development of the specific pulsation in such a manner that the specific pulsation is developed, resonance effect of a Helmholtz resonator takes place in the damper chamber.

1. A device for reducing pulsation in a variable displacement compressor, wherein the compressor is connected to an external refrigerant circuit, the compressor comprising:
 a compressor housing having a crank chamber, a suction chamber, a discharge chamber and a plurality of cylinder bores; 
 a plurality of pistons slidably received in the respective cylinder bores; and 
 a reciprocating mechanism provided in the crank chamber for reciprocating the pistons in the cylinder bores, wherein as the pistons are reciprocated, refrigerant gas in the suction chamber is drawn into the cylinder bores for compression and the compressed refrigerant gas is discharged into the discharge chamber, 
 wherein pressure in the crank chamber is controlled to vary a discharge amount of the refrigerant gas; 
 the device for reducing pulsation comprising: 
 a suction passage formed in the compressor housing, wherein the suction chamber communicates with the external refrigerant circuit through the suction passage; 
 a control valve disposed in the suction passage for controlling opening of the suction passage, the control valve comprising: 
 a valve housing disposed in the compressor housing; 
 a spool valve slidably disposed in the valve housing, wherein the spool valve has formed therethrough a flow hole, wherein pressure in the suction passage acts on the spool valve to move the spool valve; 
 a damper chamber provided in the valve housing, wherein the damper chamber communicates with the suction passage adjacent to the external refrigerant circuit through the flow hole, 
 a back pressure valve slidably disposed in the valve housing, wherein the back pressure valve is located in a facing relation to the spool valve so that the damper chamber is formed between the back pressure valve and the spool valve, wherein the pressure in the crank chamber acts on the back pressure valve to move the back pressure valve; 
 a compression spring disposed in the damper chamber for urging the spool valve and the back pressure valve away from each other; and 
 a releasing hole formed through the valve housing for releasing the refrigerant gas from the damper chamber, 
 wherein a communication passage is formed in the compressor housing, wherein the releasing hole communicates with the suction chamber through the communication passage, 
 wherein an opening between the releasing hole and the damper chamber is variable so as to be fully closed and fully opened by the movement of the back pressure valve, 
 wherein effective cross-sectional area and effective length of the flow hole are determined based on frequency of a specific pulsation of the refrigerant gas and volume of the damper chamber at the time of the development of the specific pulsation in such a manner that when the specific pulsation is developed, resonance effect of a Helmholtz resonator takes place in the damper chamber, 
 wherein the effective cross-sectional area and the effective length of the flow hole are determined based on frequency of the specific pulsation of the refrigerant gas and the total volume of the damper chamber at the time of the development of the specific pulsation, the suction chamber, the releasing hole and the communication passage. 
 
     
     
       2. The device for reducing pulsation according to  claim 1 , wherein the following equation is satisfied:
     f=c/ 2π√( S/LV )
 
 where 
 f=the frequency of the specific pulsation, 
 V=the volume of the damper chamber at the time of the development of the specific pulsation, 
 S=the effective cross-sectional area of the flow hole, 
 L=the effective length of the flow hole, and 
 c=speed of sound determined based on temperature of the refrigerant gas. 
 
     
     
       3. The device for reducing pulsation according to  claim 1 , wherein the valve housing has a cylindrical upper portion and a cylindrical lower portion, wherein the upper portion of the valve housing has inside and outside diameters that are greater than those of the lower portion. 
     
     
       4. The device for reducing pulsation according to  claim 3 , wherein the upper portion is provided with an opening through which the suction passage is formed, wherein diameter of the opening of the upper portion is larger than that of the releasing hole. 
     
     
       5. The device for reducing pulsation according to  claim 3 , wherein a cylindrical cap is provided in the upper portion adjacent to the external refrigerant circuit, wherein the cap adjacent to the spool valve serves as a stop. 
     
     
       6. The device for reducing pulsation according to  claim 3 , wherein the valve housing has formed between the upper potion and the lower portion thereof an annular projection extending radially inwardly, wherein the annular projection serves as a stop.